This application claims priority from Japanese patent application of Ogawa et al., filed on Jan. 11, 2001, No. 2001-4126, the complete disclosure of which is hereby incorporated into the present application by this reference.
1. Field of the Invention
The present invention relates to an airbag used in a head protecting airbag device to be mounted on an automobile, and to its wrapping method. Specifically, the airbag of the present invention comprises an airbag itself and a wrapping material for keeping the airbag body in a folded state. This airbag body is folded and housed on the peripheral edge of an opening on the inner side of the car body and is extended/inflated when an inflating gas flows thereinto, so as to cover the inner side opening. The wrapping member prevents the folded airbag body from returning to its unfolded state. The wrapping member is wrapped around the airbag body when folded, and in this wrapped condition this airbag body is housed in the vehicle. This wrapping member is ruptured when the airbag body is inflated.
2. Description of the Related Art
In the airbag of the head protecting airbag device of this kind of the prior art, as disclosed in Unexamined Published Japanese Patent Application No. 32153/1999, a folded airbag body is wrapped by a wrapping member keeping the folds from shifting. This wrapping member is made of a tape member or the like. Without this wrapping member, the airbag body, after being folded up, returns to its unfolded state to expand in bulk because of the spring-back mechanism. Moreover, the airbag body loses its folded-up configuration so that it cannot be mounted in the vehicle.
However, the airbag body is folded up into a rod-like shape and the wrapping member of the prior art is wrapped around the airbag body perpendicularly to the air bag""s axis. Moreover, a plurality of wrapping members is intermittently wrapped at several places along the axial direction of the folded airbag body.
In the airbag body of the prior art, specifically, the portions wrapped by the wrapping members and the portions not wrapped are alternate along the axial direction of the airbag body. It is, therefore, impossible to prevent the unwrapped portions of the airbag body from bulging due to the spring-back. As a result, there arises a problem that the airbag body cannot be mounted in the narrow housing portion provided in the vehicle.
Here, it is conceivable to wrap the airbag body with a bag (cylindrical) wrapping member so that the airbag body may be able to keep its folded-up state substantially all over its length. In this case, however, it takes a long time to insert the folded airbag body into the wrapping member having a small diameter. Alternatively, if the wrapping member has a sufficient internal diameter, it is necessary to reduce the diameter of the wrapping member itself after the folded airbag body is inserted into the wrapping member. This work has to be made on substantially all along the length of the airbag body and is troublesome.
The present invention has been conceived to solve the above-specified problems. Specifically, the present invention contemplates to provide an airbag which can remain in proper folded-up state substantially all along its length with a simple wrapping operation, and a wrapping method of the airbag.
According to the present invention, there is provided an airbag comprising: an airbag body; and a wrapping member made tearable for preventing the airbag body from being losing proper folded shape. The airbag body is folded and housed on the peripheral edge of an opening on the inner side of a car body, and folded up into a rod-like shape so that it may be extended/inflated when an inflating gas flows thereinto so as to cover the opening, and is then wrapped with the wrapping member. Moreover, the wrapping member is made of a flexible long material and is wrapped around the outer periphery of airbag body perpendicularly (obliquely) to the air bag""s axis substantially all along its length.
In the airbag according to the present invention, the long wrapping member is not intermittently arranged along the axial direction of the airbag body folded into rod-like shape. Specifically, the wrapping member is wrapped on the outer periphery substantially all along the length of the folded airbag body obliquely to the air bag""s axis. In this way, at least one portion of the wrapping member restrains the folded airbag body substantially all along the length of the airbag, and therefore the wrapping member restrains the outer periphery of the airbag body. As a result, the airbag body can be kept compactly folded up uniformly along the axial direction of the airbag body. Moreover, because the wrapping work is done helically along the outer periphery of the airbag body obliquely to the axial direction of the airbag body, it can be simply done.
In the airbag according to the present invention, therefore, the compactly folded-up state of the airbag body can be maintained uniformly substantially all over the airbag body by a simple wrapping operation.
Where the wrapping member includes a plurality of wrapping members, moreover, it is desired that the wrapping members are so wrapped on the outer periphery of the folded airbag body as to intersect with each other.
With this construction, the wrapping members are so wrapped on the outer periphery of the airbag body as to intersect with each other. Besides the intersecting portions, therefore, the outer periphery around the axis of the airbag body is restrained at a number of separated places corresponding to amount of wrapping members. As a result, it is possible to keep the more compactly folded-up state of the airbag body.
In this case, moreover, it is desired that the plurality of wrapping members wrapped on the upper side of the outer periphery of the folded airbag body be so arranged that there are different wrapping members at neighboring intersections.
With this construction, even if one wrapping member is cut, the remaining wrapping members hold the cut wrapping member on the two sides across the cut portion. Therefore, the cut wrapping member can be prevented from being loosened all over the length of the airbag body, thereby keeping the airbag body wrapped.
Moreover, it is desired that the airbag body includes a plurality of mounting portions arranged along the axial direction of the folded airbag body, for mounting the airbag body on the car body, and that the wrapping member is wrapped on the outer periphery of the folded airbag body at positions removed from the mounting portions.
If the wrapping member is wrapped on the outer periphery of the folded airbag body at positions removed from the individual mounting portions, more specifically, the individual mounting portions do not interfere with the wrapping member. Therefore, the airbag can be smoothly mounted on the car body by using the individual mounting portions. In this case, the wrapping member may be either wrapped on the airbag body while avoiding the mounting portions or partially cut at the positions of the mounting portions.
Moreover, it is desired that an adhesive is applied to the wrapping member.
With this construction, the wrapping member can be adhered to the airbag body or the like. Moreover, the wrapping member is not released from wrapping the airbag body even if partially cut.
Moreover, the wrapping member optionally includes a plurality of wrapping members intersecting each other, and the adhesive applied individually to the wrapping members adheres the wrapping members at the intersecting portions to each other. In this case, the end portions of the wrapping member need not be jointed to the airbag body so that its terminal treatment is facilitated. Especially where the silicone coating agent for imparting the heat resistance to the airbag body is applied to the outer surface of the airbag body so that the wrapping member having the adhesive applied thereto is not adhered to the airbag body, the wrapping member continues to restrain the airbag body even if partially cut.
For the treatments of ends of the wrapping members, even if the adhesive is not applied to the wrapping member, of course the terminal portions of the wrapping member may be fixed on the airbag body by a tearable tape member to be wound on the folded airbag body.
Moreover, the wrapping member may also be attached by sewing at positions where it is not exposed to the inner side of the car when the airbag body is extended/inflated.
With this construction, the wrapping member is jointed at the stitched portions to the airbag body even if the wrapping is ruptured when the airbag body is extended/inflated. Therefore, the wrapping member can be prevented from scattering into the car compartment. Moreover, the stitched portions are not exposed to the car compartment when the airbag body is extended/inflated. Therefore, the wrapping member after being cut can be prevented as much as possible from contacting with the passenger.
Moreover, it is arbitrary that the pitch at which the wrapping member is wrapped on the airbag body is changed along the axial direction of the folded airbag body.
With this construction, the pitch for the wrapping member to wrap can be narrowed at the thick portions of the folded airbag body or the portions spring-back tends to occur so as to reliably keep those portions compact. Alternatively, the pitch to wrap the wrapping member can be widened to keep the wrapping member away from interfering with the mounting portions for mounting the airbag body on the car body.
According to the present invention, there is provided an airbag wrapping method for a wrapping member to prevent shifts in folds of the airbag by using a wrapping device. The airbag body is folded and housed on the peripheral edge of an opening on the inner side of a car body and is folded up generally into a rod shape so that it may be extended/inflated when an inflating gas flows thereinto so as to cover the opening. The wrapping member is made of a flexible and tearable long material and is helically wrapped on the outer periphery substantially all over the length of the airbag folded up generally into the rod shape, by using the wrapping device. The wrapping device includes a through hole and holding members arranged around the through hole for revolving around the through hole, and holding the wrapping member but able to spool off the same to the through hole. During the wrapping, moreover, the wrapping member is wrapped on the outer periphery of the airbag body by revolving the holding members around the circumference of the through hole while spooling off the wrapping member and by inserting the airbag in the completely folded state progressively along the axial direction of the airbag through the through hole.
In the wrapping method according to the present invention, the holding members are revolved around the through hole while spooling off the wrapping member. Moreover, the airbag in the completely folded state is inserted progressively along the axial direction thereof through the through hole. Then, the individual airbag bodies can be wrapped helically on their outer peripheries with the wrapping member. Moreover, the wrapping member is not cut during the wrapping work but can wrap the continuing individual airbag bodies. In other words, the continuous wrapping member need neither be cut nor be jointed at their terminals individually to the second and succeeding airbag bodies. Merely by inserting the succeeding airbag bodies succeeding the leading airbag body into the through hole, moreover, the continuing wrapping members are sequentially wrapped on the succeeding airbag bodies. Therefore, the wrapping work can be done very efficiently.